5. If hypertrophy is your goal, eliminating the stretch-shortening cycle will do more to recruit additional muscle fibers than almost anything else you can do.

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maybe this will help?

http://en.wikipedia.org/wiki/Stretch_shortening_cycle
"As a muscle lengthens, it contracts and produces elastic energy. The force applied to the muscle increases. The muscle then contracts concentrically. The muscle shortens and the energy that has been stored dramatically increases the force of the contraction.

During the eccentric contraction, the muscle stores elastic energy. Muscular tension increases. The elastic energy that has been stored is available for powerful, dynamic movements. By stretching the muscle before it contracts, the muscle contracts with greater force. A consistent plyometric training program will increase the efficiency of the stretch-shortening cycle.